Palm Date Fibers: Analysis and Enzymatic Hydrolysis

Waste palm dates were subjected to analysis for composition and enzymatic hydrolysis of their flesh fibers. The fruit contained 32% glucose and 30% fructose, while the water-insoluble fibers of its flesh consisted of 49.9% lignin and 20.9% polysaccharides. Water-insoluble fibers were settled to 55% of its initial volume in 12 h. The presence of skin and flesh colloidal fibers results in high viscosity and clogging problems during industrial processes. The settling velocity of the fibers was improved by enzymatic hydrolysis. Hydrolysis resulted in 84.3% conversion of the cellulosic part of the fibers as well as reducing the settling time to 10 minutes and the final settled volume to 4% of the initial volume. It implies easier separation of the fibers and facilitates fermentation processes in the corresponding industries. Two kinds of high- and low-lignin fibers were identified from the water-insoluble fibers. The high-lignin fibers (75% lignin) settled easily, while the low-lignin fibers (41.4% lignin) formed a slurry suspension which settled very slowly. The hydrophilicity of these low-lignin fibers is the major challenge of the industrial processes

Moisture sorption isotherms and isosteric heat of sorption of dry persimmon leaves

Moisture sorption isotherms of persimmon leaves were determined at 20, 30 and 40 °C using the standard gravimetric static method over a range of relative humidity from 0.06 to 0.9. The experimental sorption curves were fitted by seven equations: Henderson, Halsey, Smith, Oswin, BET, GAB and Caurie. The Halsey, Smith, GAB and BET models were found to be the most suitable for describing the sorption curves. The isosteric heat of sorption of water was determined from the equilibrium data at different temperatures. It decreased as moisture content increased and was found to be a polynomial function of moisture content.The authors acknowledge the support of the Universtitat Politecnica de Valencia.Martínez Las Heras, R.; Heredia Gutiérrez, AB.; Castelló Gómez, ML.; Andrés Grau, AM. (2014). Moisture sorption isotherms and isosteric heat of sorption of dry persimmon leaves. Food Bioscience. 7:88-94. doi:10.1016/j.fbio.2014.06.002S8894

Optimization of cultural factors influencing the production of extracellular vesicles and proteinase by Pseudomonas fragi ATCC 4973

Pseudomonas fragi ATCC 4973 was grown in trypticase soy broth (TSB), on a trypticase soy broth + 1.5% agar (TSA) surface, and in a defined citrate broth. The citrate broth contained glutamine as the sole nitrogen source, Pseudomonas fragi grown in TSB started proteinase production at 24 h, during the late logarithmic early stationary growth phase. Pseudomonas fragi grown on TSA surfaces initiated proteinase production at 4 h, 20 hours earlier than in liquid medium. Electron micrographs of P. fragi grown on TSA revealed extracellular vesicles ca. 20 nm in diameter "blebbing" off the surface of the cells. These vesicles were absent from the surface of P. fragi cells grown in TSB, although vesicles could be isolated from the culture supernatant. Isolated extracellular vesicles were ca. 20 nm in diameter and contained a proteinase similar to that found in the supernatant. Electrophoretic analysis showed the vesicles and outer cell membrane of P. fragi to share similarities in their composition. Use of the centroid search technique of Aishima and Nakai, showed the optimum cultural conditions for proteinase production by P. fragi, in defined citrate broth to be: incubation temperature, 12.5 C; incubation time, 38 h; initial pH, 6.8; organic nitrogen concentration, 314 mmole nitrogen/L (glutamine); a gas mixture containing 16.4% oxygen flowing over the medium (7.42 ppm dissolved oxygen). Oxygen was the major factor influencing proteinase production by P. fragi. A comparison of optimization techniques suitable for microbiological experiments showed that the centroid search technique of Aishima and Nakai, the modified super simplex of Nakai and Kaneko and the simplex technique of Morgan and Deming all required similar time and experiment numbers to obtain the optimum point.Land and Food Systems, Faculty ofGraduat